Paper feed table lifting device for a printing press

ABSTRACT

A lifting device for a paper feed table for a printing press which operates to lift a table, by rotation of a pinion meshing with a rack connected to the table and disposed substantially vertically, when the height of a stack of printing sheets on the feed table is decreased during printing. A ratchet wheel is rotatable with the pinion and a pawl means is movable into and out of engagement with the ratchet wheel, for intermittently rotating the latter. The pawl means normally is retained out of engagement with the ratchet wheel, and is brought into engagement therewith only responsive to a predetermined reduction in the height of the stack of sheets on the printing table. Thereupon, the feed table is lifted through a distance corresponding to the reduction in the height of the stack of sheets thereon.

I United States Patent 11s; 3,667,385 Suzuki 51 June 6, 1972 1541 PAPER FEED TABLE LIFI'ING DEVICE 3,214,165 10/1965 Warner ..27l/62 FOR A PRINTING PRESS Ex R be E Pu" Primary aminero rt rey [72] inventor: Minor-u Suzuki, Kanagawa-ken, Japan ASH-am Examiner j Reed Fisher 73 Assignee: Kabushiki-Kaisha Ricoh, Tokyo, Japan Attorney-Mom and Town [22] Filed: 0d. 8, 1969 57 ABSTRACT [2H P 864,830 A lifting device for a paper feed table for a printing press which operates to lift a table. by rotation of a pinion meshing [30] Foreign Appficafion priority Data with a rack connected to the table and disposed substantially venically, when the height of a stack of printing sheets on the Oct. 1], 1968 Japan ..43/74443 feed tab'e is dcreased i g i i g A- ratchet wheel is 1 rotatable with the pinion and a pawl means is movable into C(iI ..101/232,271 39 and out of engagemcm with the ratchet wheel, for imermib tently rotating the latter. The pawl means normally is retained [58] held of Search 18 33 out of engagement with the ratchet wheel, and is brought into I engagement therewith only responsive to a predetermined Reerenm Cited reduction in the height of the stack of sheets on the printing UNITED STATES PATENTS 415,877 [1889 Ross ..27l/62 Greene ..27l/62" table. Thereupon, the feed table is lifted through a distance corresponding to the reduction in the height of the stack of sheets thereon.

5 China, 6 Drawing Figures PATENTEBJUH 6 m2 3, 667, 385

- SHEET 1 or 2 FIG 2 (PI/0E Aer) INVENTOR MIA 0R U SUZUKI ATTORNEYS PATENTEDJUH 6|972 A 3,667,385

. SHEET 2 BF 2 INVENTOR M/NJAU Sl/Zl/K/ ATTORNEYS PAPER FEED TABLE LIFIING DEVICE FOR A PRINTING PRESS BACKGROUND OF THE INVENTION In one type of printing press, known in the art, a stack of printing sheets is piled on a paper feed table and the sheets are successively fed to the printing cylinder. In such printing press, it is necessary that a paper feed roller bear against the stack of printing sheets under a suitable pressure, and it is necessary to maintain the top of the stack of sheets at a suitable level so that the printing sheets may be fed smoothly. This requirement generally is met by lifting the paper feed table as the height of the stack of sheets is decreased.

FIGS. 1 and 2 illustrate an example in which a paper feed table is lifted in a conventional manner. Referring to FIG. 1, a ratchet wheel I mounted on a shaft is formed integrally with a pinion 28 meshing with a rack 33 extending vertically of a side plate 38a of a paper feed table 38. A pawl 2a is pivoted at 34 to the free end of a pivoted pawl lever 2 oscillated by a cam 35 rotatable in conjunction with a printing cylinder, and is biased at all times into engagement with the teeth of ratchet wheel 1. Responsive to each oscillation of lever 2, ratchet wheel 1 is advanced a distance corresponding to the spacing of two teeth, and is held in check, against reverse rotation, by a pawl 3. Pawl 2a is maintained constantly in frictional engagement with the teeth of ratchet wheel I.

As the printing operation progresses, the number of printing sheets 36 stacked on feed table 38 is reduced, thus reducing the height of the stack. When the height of the stack has been reduced a predetermined amount, a stop 37 descends a distance corresponding to the reduction in the height of the stack, with the result that the range of pivotal movement of lever 2 is increased and pawl 2a advances ratchet wheel 1, as best seen in FIG. 2b. Thereby, rack 33 is lifted a distance corresponding to the reduction in the height of the stack of printing sheets on feed table 38, as a result of rotation of pinion 28 as a unit with ratchet wheel 1. The upward movement of rack 33 lifts feed table 38 to a position in which printing sheets 36.

can be fed smoothly to the printing cylinder.

The prior art arrangement shown in FIGS. 1 and 2 have certain disadvantages. A variation in the range of pivotal movement of pawl lever 2, caused by a reduction in the level of the uppermost sheet of the stack of printing sheets 36, is not necessarily proportional to the reduction in the level of the uppermost sheet. Consequently, the degree of angular movement of ratchet wheel 1 may not be in confonnity with the reduction in the level of the uppermost sheet. Furthermore, since pawl 2a is maintained in engagement with ratchet wheel I at all times, a backlash of ratchet wheel 1, relative to pawl 3, may occur as shown in FIG. 2c, so that pawl 2a often pushes and moves the same ratchet wheel tooth several times. This causes play to occur in the vertical position of paper feed table 38.

SUMMARY OF THE INVENTION This invention relates to lifting devices for paper feed tables of printing presses or the like and, more particularly, to a lifting device in which play, in the vertical direction of movement of the feed table, is eliminated.

In accordance with the invention, a lifting device for a paper feed table comprises a pawl which is normally maintained out of engagement with a ratchet wheel meshing with a rack secured to the feed table, but which is arranged to engage the ratchet wheel when the feed table is to be lifted. The lifting device includes a mechanism which senses a predetermined variation in the level of the uppermost sheet of the stack of printing sheets, and transmits the information to the pawl lever.

An object of the invention is to provide an improved lifting device for a paper feed table for printing presses or the like.

Another object of the invention is to provide such a lifting device in which play, in a vertical movement of the lifting table, is prevented.

For an understanding of the principles of the invention, reference is made to the following description of a typical embodiment thereof as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings 1 FIG. 1 is a schematic side view of essential portions of a drive section of a conventional paper-feed table lifting device for printing presses;

FIG. 2 shows the manner of operation of the essential por-' DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 3, a stack 1, of printing sheets, rests on a paper feed table (not shown) and a paper feed roller 32 bears against the uppermost sheetunder a suitable force. A vertically oriented rack means 43'is connected to opposite sides of the paper feed table. Paper feed roller 32 is mounted on a shaft 4 which is rotatably supported, at opposite ends, by a pair of roller support plates 5 secured to a rotary shaft 6 rotatably supported by opposite side plates 39 of a printing press. Rack means 43 comprises racks 43a which mesh with pinions 8 secured to a shaft 7 which is rotatably supported, at opposite ends, by side plates 39. A ratchet wheel 9 is secured to the outer end of shaft 7.

A shaft 10 is secured to one of the side plates 39, which plate is formed with an opening A,- and shaft 10 pivotally supports a folower lever 11 having a shaft 11b at its free end rotatably supporting a roller 11a A pivot 11c intermediate to the ends of follower lever l l pivotally supports a pawl means 12. Follower lever 11 normally is biased, by a suitable spring which has not been shown, to swing about shaft 10 in the clockwise direction as viewed in FIG. 3. Thus, roller Ila is constantly pressed against a cam 14 secured to a drive shaft 13 rotatably supported by side plates 39, so that roller 11a causes follower lever 11 to oscillate as cam l4 rotates. Shaft 13 is rotatable with the printing cylinder. I

Pawl means 12 has a first arm projecting laterally and bent at its forward end to form a pawl 12a arranged to engage the teeth of ratchet wheel 9. Pawl means 12 also has a second arm 12b which projects downwardly and which is connected to one end of a spring 15 normally biasing pawl means 12 to swing clockwise as viewed in FIG. 3

A first pivotal member 16 is formed, at its forward end, with a bent portion 16a (FIG. 6) which extends through opening A into contact with a lower end edge 5a of one of the roller support plates 5. Member 16 is evidently mounted at the outer end of shaft 10. A second pivotal member-17 is also pivotally mounted at the outer end of shaft 10, and is formed with a hook 17a for engaging a lower end of second arm 12b of pawl means 12, and member 17 is biased, by a suitable spring which has not been shown, to swing in the counterclockwise direction. The first pivotal member 16 has a projection 16b pivotally supporting an intermediate pivotal member 18 on a pivot 16c.

lnterrnediate pivotal member 18 has a projection 18a connected by a spring 19 to an ear 16d of first pivotal member 16. Thus intermediate pivotal member 18 is biased by spring 19 to swing about pivot in the counterclockwise direction. Member 18 has one arm 18b which is pressed against an abutment 20a of a stop 20 secured to one of the side plates 39, and member 18 has another arm which is pressed against a contact portion 17b of the second pivotal member 17. Thus, hook 17a of member 17 is thereby moved upwardly. Pivotal movement of member 17 by arm 180 of member 18 is limited by a pin 21 secured to a side plate 39.

When feed roller 2 is in a normal position, as shown in FIG. 3, hook 17a of second pivotal member 17 holds the second arm 12b of pawl means 12 in check. Thus, movement of follower lever 11, effected by rotation of cam 14, from the position shown in FIG. 3 to the position shown in FIG. 4, will not bring pawl 12a of pawl means 12 into engagement with ratchet wheel 9.

Since rack means 43 tends to move downwardly under the weight of the paper sheets and under its own weight, ratchet wheel 9 normally is urged to rotate in a counterclockwise direction, as viewed in FIG. 3 Such counterclockwise rotation of ratchet wheel 9 is prevented by engagement of the teeth of ratchet wheel 9 with a bent portion 220 of a reverse rotation stop or pawl 22 pivoted on one of the side plates 39. Stop pawl 22 has a projection 22b connected by a spring 23 to a side plate 39, so that stop pawl 22 is biased to move in the clockwise direction so that bent portion 22a is maintained in engagement with a tooth of ratchet wheel 9. Spring 15, which has one end connected to second arm 12b of pawl means 12, has its other end connected to an arm 22c of stop pawl 22.

In operation, as printing sheets are fed successively to the printing cylinder and as paper feed roller 32 moves downwardly a distance corresponding to the reduction in the height of the stack of paper sheets, roller support plates are pivoted in the counterclockwise direction so that, through their lower edges 5a, the bent portion 16a of first pivotal member 16 is moved to cause member 16 to pivot counterclockwise about pivot shaft 10. The counterclockwise movement of first pivotal member 16 causes intermediate pivotal member 18 to move in a clockwise direction about the point of engagement between its arm 18b and the upper portion 20a of stop 20. Thereby, the pressure of the other arm 18c of member 18 against contact edge 17b of second pivotal member 17 is released. Member 17 thus moves counterclockwise about shaft 10 to follow the swinging movement of member 18 in a clockwise direction. As a result, second arm 12!: of awl means 12 is released from engagement with hook 17a of second pivotal member 17, as illustrated in FIG. 5, so that pawl 12a of pawl means 12 is engaged with one of the teeth of ratchet wheel 9 under the bias of spring 15. By virtue of the oscillation of follower lever 11 by cam 14, pawl means 12 is thus caused to rotate ratchet wheel 9 clockwise as viewed in FIGS. 3, 4 and 5. Clockwise rotation of ratchet wheel 9 effects, through pinion 8 and rack 43, upward movement of rack means 43 and the paper feed table which operates substantially as a unit with the rack means. The paper feed table is moved upwardly a distance corresponding to the reduction in the height of printing sheets on the paper feed table.

When the paper feed table is thus moved upwardly, paper feed roller 32 is restored to its normal position as are also the plates 5 so that the lower end edges 5a of the plates are released from pressure engagement with the bend portion 16a of first pivotal member 16. This allows member 16 to pivot clockwise about shaft 10, and intermediate pivotal member 18 to pivot about the point of contact between itself and the portion 20a of stop 20, in the counterclockwise direction. Arm 18c of member 18 pushes upwardly contact edge 17b of member 17. This causes member 17 to pivot clockwise about shaft 10, thereby bringing hook 17a to a position in which it is engageable with second arm 12b of pawl means 12, as viewed in FIG. 4.

, Pawl means 12 has an upwardly directed arm which is formed, at its forward end, with a bent portion 120 arranged to abut a flange 13a of a bearing journaling shaft 13. Hook 17a and second arm 12b, which are disengaged from each other responsive to a predetermined reduction in the height of the stack of printing sheets on the paper feed table, are reengaged with each other after the paper feed table has been moved upwardly. This occurs when follower lever 11 is pivoted to its rightmost position by following movement of cam 14. If follower lever 11 is pivoted to the right, or clockwise, then end portion 120 of pawl means 12 abuts flange 13a. The result of this is that pawl means 12 is positioned as if it had pivoted counterclockwise about the point of engagement of bent portion and flange 13a. This causes hook 17a to engage the lower end of second arm 12b of pawl means 12.

As illustrated in FIG. 3, stop 20 is formed with a slot 20b through which there extend screws 20c and 20d securing the stop to a side plate 39. it will be noted that the point of contact between arm 18a of intermediate pivotal member 18 and portion 20a of stop 20 can be adjusted, within the limits of stop 20b, by loosening screws 20c and 20d and then retightening the screws.

From the foregoing description, it will be clear that the lifting device embodying the invention is so constructed that pawl means 12, supported by follower lever 11, for operating ratchet wheel 9, is brought into abutting engagement with ratchet wheel 9 only when the pawl means is operated to actuate the ratchet wheel, and is maintained out of engagement with ratchet wheel 9 when it is inoperative to actuate ratchet wheel 9. This eliminates vertical play of the paper feed table and reduces wear and tear on ratchet wheel 9 and pawl 12a of pawl means 12. The lever mechanism, consisting of first pivotal lever 16, second pivotal lever 17 and intermediate pivotal lever 18, can sense and transmit, to pawl means 12, a variation in the position of paper feed roller 32 caused by a predetermined reduction in the height of the stack of printing sheets on he paper feed table, whereby the height of the stack can be constantly maintained at a suitable level.

Additionally, when the stack of printing sheets is exhausted, it has hitherto been customary to disengage both the pawl and the reverse rotation preventing stop from the ratchet wheel and then to move the paper feed table downwardly. In the lifting device embodying the invention, it is necessary only to disengage reverse rotation preventing stop 22 from ratchet wheel 9, because pawl means 12 normally is held out of engagement with ratchet wheel 9. This facilitates supplementing the stack of printing sheets.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise such principles.

What is claimed is:

1. In a lifting device for a paper feed table supported, for substantially vertical movement, on a printing press having a printing cylinder, the feed table supporting a stack of sheets to be printed, feed means engageable with the sheets to feed the sheets to the press and resulting in a reduction of the height of the stack on the table, and lifting means operable, responsive to a reduction of the height of the stack, to lift the feed table to compensate for such reduction; the improvement comprising,

without departing from in combination, rack means secured to said table and extend ing substantially vertically; rotatable pinion means meshing with said rack means; a ratchet wheel secured for rotation with said pinion means; a cam rotatable with said printing cylinder; a pivotally mounted follower lever oscillatable by said cam; pawl means pivotally mounted on said follower lever for oscillation by the latter; means biasing said pawl means to engage said ratchet wheel to rotate the latter in a direction to lift said rack means; means engaged with said ratchet wheel and preventing reverse rotation thereof; releasable latch means normally engaged with said pawl means and pivoting said pawl means to a position in which said pawl means is inoperative to engage said ratchet wheel during oscillation of said follower lever; release means operatively associated with said latch means and operable by said feed means, responsive to a predetermined reduction of the height of said stack, to

release said latch means for pivoting of said pawl means to engage said ratchet wheel during oscillation of said follower lever; and means operable, responsive to a preset upward movement of said feed table to reengage said latch means with said pawl means.

2. In a lifting device for a paper feed table, the improvement claimed in claim 1, in which said pawl means has a first arm extending toward said ratchet wheel and formed with a pawl on its free end engageable with said ratchet wheel, and a second arm extending at an angle to said first arm; said releasable latch means comprising a pivotal member formed with a hook portion engageable with said second arm.

3. In a lifting device for a paper feed table, the improvement claimed in claim 1, in which said feed means is a sheet feeding roller mounted for movement downwardly in accordance with the reduction in height of said stack; said release means cmprising a first pivotal member operable to detect a predetermined downward movement of said feed roller, and an intermediate pivotal member pivotally supported, intermediate its ends, by said first pivotal member and having an end engaging a stop for pivotal movement of said intermediate pivotal member about said stack as a fulcrum; said releasable latch means comprising a second pivotal member engaged with the other end of said intermediate pivotal member for pivoting by the latter and formed with a hook engageable with said pawl means and disengageable from said pawl means, by pivoting of said second pivotal member by said intermediate pivotal member, when said first pivotal member detects a predetermined downward movement of said feed roller.

4. In a lifting device for a paper feed table, the improvement claimed in claim 2, in which said pawl means has a third arm formed with a bent portion at its free end engageable, during oscillation of said follower lever, with a fixed stop to form a fulcrum for pivoting of said pawl means on said follower lever in a direction to provide for engagement of said hook with said second arm of said pawl means.

5. In a lifting device for a paper feed table, the improvement claimed in claim 3, including means mounting said stop for'adjustment. 

1. In a lifting device for a paper feed table supported, for substantially vertical movement, on a printing press having a printing cylinder, the feed table supporting a stack of sheets to be printed, feed means engageable with the sheets to feed the sheets to the press and resulting in a reduction of the height of the stack on the table, and lifting means operable, responsive to a reduction of the height of the stack, to lift the feed table to compensate for such reduction; the improvement comprising, in combination, rack means secured to said table and extending substantially vertically; rotatable pinion means meshing with said rack means; a ratchet wheel secured for rotation with said pinion means; a cam rotatable with said printing cylinder; a pivotally mounted follower lever oscillatable by said cam; pawl means pivotally mounted on said follower lever for oscillation by the latter; means biasing said pawl means to engage said ratchet wheel to rotate the latter in a direction to lift said rack means; means engaged with said ratchet wheel and preventing reverse rotation thereof; releasable latch means normally engaged with said pawl means and pivoting said pawl means to a position in which said pawl means is inoperative to engage said ratchet wheel during oscillation of said follower lever; release means operatively associated with said latch means and operable by said feed means, responsive to a predetermined reduction of the height of said stack, to release said latch means for pivoting of said pawl means to engage said ratchet wheel during oscillation of said follower lever; and means operable, responsive to a preset upward movement of said feed table to reengage said latch means with said pawl means.
 2. In a lifting device for a paper feed table, the improvement claimed in claim 1, in which said pawl means has a first arm extending toward said ratchet wheel and formed with a pawl on its free end engageable with said ratchet wheel, and a second arm extending at an angle to said first arm; said releasable latch means comprising a pivotal member formed with a hook portion engageable with said second arm.
 3. In a lifting device for a paper feed table, the improvement claimed in claim 1, in which said feed means is a sheet feeding roller mounted for movement downwardly in accordance with the reduction in height of said stack; said release means comprising a first pivotal member operable to detect a predetermined downward movement of said feed roller, and an intermediate pivotal member pivotally supported, intermediate its ends, by said first pivotal member and having an end engaging a stop for pivotal movement of said intermediate pivotal member about said stack as a fulcrum; said releasable latch means comprising a second pivotal member engaged with the other end of said intermediate pivotal member for pivoting by the latter and formed with a hook engageable with said pawl means and disengageable from said pawl means, by pivoting of said second pivotal member by said intermediate pivotal member, when said first pivotal member detects a predetermined downward movement of said feed roller.
 4. In a lifting device for a paper feed table, the improvement claimed in claim 2, in which said pawl means has a third arm formed with a bent portion at its free end engageable, during oscillation of said follower lever, with a fixed stop to form a fulcrum for pivoting of said pawl means on said follower lever in a direction to provide for engagement of said hook with said second arm of said pawl means.
 5. In a lifting device for a paper feed table, the improvement claimed in claim 3, including means mounting said stop foR adjustment. 